In offshore oil production much use is made of floating production vessels which are stationed in the vicinity of submarine wellheads. Oil produced in the wells is delivered from the wellheads to the vessel through flexible hoses. The hoses are required to be flexible because the floating vessels are subject to significant dynamic motion and displacement from their nominal position due to the action of wind, wave and current and a continuity in the fluid transfer must be maintained despite such displacements of the vessel.
In many instances, the nominal position of the vessel is maintained by so-called single point mooring systems, which allow the vessel to weathervane to take up a natural heading which offers the least resistance to wind, wave and current.
In many situations, the depth of water beneath the keel of the vessel is sufficient to allow a sufficiently slack flexible hose system to be fitted. Consequently, the hose system can follow all the vessels movements and displacements as afforded by the single point mooring system, by simply adjusting its configuration.
However, in very shallow depths of water this is not always the case and it may not be possible to provide a sufficiently long and slack flexible hose to accommodate the movements of the vessel. Therefore, the hose system may become too extended and damage to it may result.
The present invention provides apparatus for transferring fluid between a point on the seabed and a floating vessel, comprising a first flexible tube providing a fluid conduit and having a first end attachable to a floating vessel and a second end; a second flexible tube providing a fluid conduit and having a first end attached to a point on the seabed and a second end attachable for fluid communication with the first tube; and a structure mounted on the seabed having a movable member mounted thereon to which the second ends of the first and second tubes are attached, the movable member beings displaceable relative to the seabed structure in response to load on the first tube exceeding a predetermined threshold.
The apparatus therefore provides additional displacement capability which prevents the first hose from becoming stretched beyond its design limit.
In a first embodiment, the movable member consists of an arm with a first end pivotally mounted to the seabed structure for rotation about the structure and a second end to which the second ends of the first and second tubes are attached.
In an alternative embodiment, the movable member consists of a body mounted to the seabed structure for linear movement relative thereto.
In this case, the seabed structure may define a guide track in which the body is slidably mounted.
The first end of the second hose may be attached to the seabed structure which carries the movable member or may be attached to a point on the seabed displaced from the seabed structure.